Microsoft Exchange Server 2010 Web Services SDK March 2010
http://www.microsoft.com/downloads/details.aspx?displaylang=en&FamilyID=155ab218-3cd5-439f-9ce3-5e6983ab6b79

The Exchange 2010 Web Services SDK assists developers who are building Web services–based applications for Exchange 2010. This release of the SDK provides new and updated information and sample code to help you develop collaborative enterprise applications for Exchange 2010. The Readme file contains installation instructions for and late-breaking information about the Exchange 2010 Web Services SDK.

Microsoft Exchange Server 2010 Transport Agents SDK March 2010
http://www.microsoft.com/downloads/details.aspx?displaylang=en&FamilyID=0df5bdff-47e2-4444-8548-1d7b861529dd

The Exchange 2010 Transport Agents SDK assists developers who are building Exchange transport agent applications for Exchange 2010. This release of the SDK provides new and updated information and sample code to help you develop collaborative enterprise applications for Exchange 2010. The Readme file contains installation instructions for and late-breaking information about the Exchange 2010 Transport Agents SDK.

Microsoft Exchange Server 2010 Backup and Restore SDK March 2010
http://www.microsoft.com/downloads/details.aspx?displaylang=en&FamilyID=6093ae54-525a-4d86-820c-31bc0c63a238

This SDK provides information about how to create applications that back up, restore, and recover Exchange 2010 databases. The SDK download also includes a 64-bit native-code library that can be used to verify the integrity of Exchange 2010 databases that are to be backed up. The Readme file contains installation instructions for and late-breaking information about the Exchange 2010 Backup and Restore SDK.